Refractory material for electric insulation and other purposes.



UNITED STATES Parana orrron.

DEMETRIUS M. STEWARD, OF CHATTANOOGA, TENNESSEE.

REFRACTORY MATERIAL FOR ELECTRIC INSULATION AND OTHER PURPOSES.

Specification of Letters Patent.

Patented March 27, 1906.

To all whom if may concern:

non-conductivity afford insulation equally against heat as againstelectricity.

Generally speaking, the substance of my present invention is a compound,a refractory material of high electrical resistance and of practicallyperfect homogeneity that is absolutely fireproof and that is unaffectedby cold or moisture. Its hardness, its stressresisting qualities, andits resistance to moisture and to the effects of heat and cold render mymaterial superior to any vitreous or amorphous insulating substance,such as rubher or the like, and render it available in many instancesunder conditions which would absolutely prohibit the employment of many,if not all, substances which have been under favorable conditionsemployed for insulating purposes.

The compound or material, by either of which terms my invention isherein. designated, is the product of a process which constitutes thesubject-,matter of a separate application for patent made by me filedMay 25, 1905, Serial No. 262,262.

The substance, which may be regarded as constituting the basis of myinventionthat is, the indispensable ingredient of itis magnesiumsilicate or aluminium silicate or a substantial equivalent of either. Intheir most familiar forms the silicates referred to have closeresemblance one to another and are found in nature in the form ofsoapstone, steatite, talc, or the like. For convenience I shallhereinafter employ the term steatite to designate conventionally allsubstances of the general description above specified or theirsubstantial equivalents, including pyrophillite.

In the manufacture of my material or compound, as herein described, Iutilize the steatite or its equivalent, as s ecified, preferably infinely comminuted or pu verulent form, and

having reduced that component by mixture with other ingredients to aplastic mass impart to such plastic mixture any desired shape. Themolding, as it maybe termed, of the plastic mixture, although, perhaps,more accurately described as shaping or modeling, is preferably effectedunder great pressure. The molding feature of the invention isparticularly important, because asidefrom and in addition to thecharacteristic qualities it imparts to the product or compound,particularly that of uniform homogeneity when it is practiced undergreat pressure, which is, as specified, always preferred, it affords animportant and valuable aid or contribution to the manufacture in generalof certain articles from steatite. The known deposits of native steatiteare not only limited, but the value of that substance in workable bulkis at present considerable and is increasing. My invention rendersequally serviceable all raw material and much which ordinarily would beesteemed waste or at any rate of inferior value. Besides that theemployment of the steatite in plastic form alone renders it possible toproduce at diminished cost articles of a shape and configurationdifferent from that in which they could be produced by the formerlyuniversal practice of cutting or carving the massive steatite it makesit possible in very many instances to produce shapes which could not inanywise be produced from the native material, as by cutting or carvingor any other of the usual methods of working it. In respect to theformer suggestion contained in the last sentence specific reference maybe had to the manufacture of steatite gas-burner tips, which althoughthey may be made and have been made of native steatite may be bettermade and cheaper from the mixture subsequently converted, which constitutes my present invention herein specified/ In respect to the lattersuggestion contained in the aforesaid sentence reference may be had notonly to the production of minute tubes of any desired lengths andpossessing certain characteristic qualities specified herein as belongjnto my material, which is rendered practicable by the use of my inventionand which cannot be arrived at in manufacture from native steatite, butalso to the manufacture of insulators of exact dimensions, which fromthe nature of the compound can be produced in my material, owing to itshomogeneity and quality ofresistanc-e without warping upon application fheatqualities not possessed by the native steatite to the same degreeor, generally speaking, to-a reliable degree In specifying theproportions of compo nents employed in my mixture I desire to have itunderstood that while magnesium silicate or aluminium silicate is thebasis as aforesaid of the compound, and therefore always introduced intothe mixture considerably in excess of any other component, some latitudeof variation is permissible without departing from the principle of myinvention, the object aimed at by change of the proportionate quantityof water-glass, as hereinafterspecified, being to vary the compositionof the material, compound, or finished product, so as to obtain thedegree of hardness and density or compactness sought.

In the manufacture of my com ound the proportions of the components 0the mixture I prefer by reason of the comparative width of range ofutility in the resultant product to use one hundred parts offinelycomminuted steatite or its equivalent, as specified, and twentyparts of water-glass t at is, sodium silicate or potassium silicate I influid form-the said partsbeing proportioned by weight.

The components specified are thoroughly .mixed in any suitable manner bymachinery or otherwise to a plastic or semi lastic mass of about theconsistency of wor able putty.

. The first'step in the treatment of the mixture is to expel orpartially expel the water it contains, "which may be accomplished bydrying it in a drying-kiln for example, one heated by steam. f

The mixture may be formed into blanks and shaped, as by cutting, afterthey are steam dried, or it may be molded or shaped while the'mixture isin the plastic state and steam dried in any desired form imparted to it.

In preparing the mixture above specified for thedryi'ng-kiln it ispreferably, as specified, reduced to a closely-compacted mass of uniformdensity throughout. This effect may be produced by subjecting the lasticf mixture to heavy pressure, as in a hy raulic press, and that treatmentis preferably resorted to whether the mixture be presented tothedrying-kiln in the form of a blank or native or massive steatite.

ual or mechanical operation necessary or desirable for the completion orfinishing of the article.

The mixture undergoes inthefinal step of the process by which thecompound is produced a radical change from its green state, and becomesexceedingly hardhard enough, it may be, by way of illustration, toscratch glass and to resistthe action of any ordinary cutting-tool. Inassing to that state the mixture ceases to e a mixture having steatitefor its basic component, andbecomes a compound. That final step of therocess is to subject the mixture, preferaby kilndried, as abovespecified, to a sufiiciently high temperature to convert it into thefinished product, material, or compound,'which is distinguishable by avariety of characteristic qualities. From among such qualities there maybe selected for enumeration the following, to, wit: The compoundpossesses the quality of resistance to moisture, it is unaffected byheat, and it may not be carbonized or ignited by intense heat,it isbelieved, even in that of any electric arc. Articles produced therefromare durable, being incomparably stronger than porcelain or any vitreousor other similar material, and of an electrical resistance that ispractically infinite, and may be manufactured at reason able cost.

The temperature at. which the change in the character of the mixture tothat of a compound occurs ma be varied somewhat. The reaction by Whicthe mixture is converted begins at about 700 centigrade and it appearsto depend upon an elevated temperature rather than upon the length oftime of exposure. Experience has shown the reaction to be complete andthe best results in the manufacture of minute articles to be obtainableat about 1,500 centigrade. 'The time of exposure may be varied and isdependent in part upon the bulk of the mass that is being treated. Inactual manufacture I employ a temperature of from 1,500 to 2,000centigrade for aperiod dependent upon tests repeated during the firing,but usually of from five to eight hours. Laboratory tests upon minutearticles have shown the best results to be obtainable by a fiveminutesexposure to a temperature of about 1,500 centigrade.

While in the foregoing specification I have indicated a choice ofmaterials as available in the preparation of the mixture from which mycompound is produced, yet I wish it to be distinctlyunderstood that Iregard magnesium silicate and sodium silicate as the unquestionablyavailable components of the,

mixture. Whatever is predicated of the of the same in the manufacture ofmy product for commercial purposes. Said mixture constitutes, therefore,the standard with Which proposed substitutions in the reparation of mymixture must be compared in order to determine their equivalency ornon-equivalency to the said components.

Articles made of my finished material may be, ifpreferred, supplied witha surface glaze by the use of magnesium or other suitable enamelsuch,for example, as that used on porcelain or kaolin Ware.

What I claim is 1. An insulating and refractory material comprising thecombination of water-glass and steatite or their substantialequivalents, chemically converted practically to a complete extent byheat.

2. An insulating and refractory material comprising the combination ofsteatite and water-glass or theirsubstantial equivalents, converted byractically complete reaction.

3. An insulating and refractory material comprising the combination ofpowdered steatite and Water-glass or their substantial equivalents,substantially in the roportions specified, converted by practical ycomplete reaction.

4. An insulating and refractory material I Luna. 4. 4

